This report summarizes the research on the System and Propagation Availability Analysis for NASA's project on Advanced Air Transportation Technologies (AATT). The objectives of the project were to determine the communication systems requirements and architecture, and to investigate the effect of propagation on the transmission of space information. In this report, results from the first year investigation are presented and limitations are highlighted. To study the propagation links, an understanding of the total system architecture is necessary since the links form the major component of the overall architecture. This study was conducted by way of analysis, modeling and simulation on the system communication links. The overall goals was to develop an understanding of the space communication requirements relevant to the AATT project, and then analyze the links taking into consideration system availability under adverse atmospheric weather conditions. This project began with a preliminary study of the end-to-end system architecture by modeling a representative communication system in MATLAB SIMULINK. Based on the defining concepts, the possibility of computer modeling was determined. The investigations continue with the parametric studies of the communication system architecture. These studies were also carried out with SIMULINK modeling and simulation. After a series of modifications, two end-to-end communication links were identified as the most probable models for the communication architecture. Link budget calculations were then performed in MATHCAD and MATLAB for the identified communication scenarios. A remarkable outcome of this project is the development of a graphic user interface (GUI) program for the computation of the link budget parameters in real time. Using this program, one can interactively compute the link budget requirements after supplying a few necessary parameters. It provides a framework for the eventual automation of several computations required in many experimental NASA missions. For the first year of this project, most of the stated objectives were accomplished. We were able to identify probable communication systems architectures, model and analyze several communication links, perform numerous simulation on different system models, and then develop a program for the link budget analysis. However, most of the work is still unfinished. The effect of propagation on the transmission of information in the identified communication channels has not been performed. Propagation effects cannot be studied until the system under consideration is identified and characterized. To study the propagation links, an understanding of the total communications architecture is necessary. It is important to mention that the original project was intended for two years and the results presented here are only for the first year of research. It is prudent therefore that these efforts be continued in order to obtain a complete picture of the system and propagation availability requirements.